Speaker: S.A. Levshakov
Institute: Key Lab. for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory & Dept. of Theoretical Astrophysics, Physical-Technical Institute, St. Petersburg
Time : May 21(Friday) 14:00pm
Place: Middle conference room, 3rd floor

Abstract:

Absorbers with high metal content (solar to oversolar) are observed in quasar spectra both as associated and as intervening systems. Due to high metallicity, lines of multiple metal ions are present and allow us to derive therelative abundances of many elements such as C, N, O, Si, Mg, Fe. In turn, these relative abundances can be used to determine the main source of the chemical enrichment (SNeI, SNeII or AGB-stars) for each system.

Among metal-rich absorbers, a sub-class characterized by low ionization parameters can be singled out. Absorbers of this class reveal an abundance pattern that relates them to AGB-stars. The number of such systems rises sharply at z ~ 1.8 which corresponds to a peak in star-forming activity and a maximum in the space density distribution of luminous quasars.